PropertyChangedDistributor

PropertyChangedDistributor.cs

using System;
using System.Collections.Generic;
using System.ComponentModel;

namespace Common {

	public sealed class PropertyChangedDistributor: IDisposable {
	
		private readonly INotifyPropertyChanged _obj;
		private readonly Dictionary<string, List<Entry>> _subscriptions = new Dictionary<string, List<Entry>>();

		public PropertyChangedDistributor(INotifyPropertyChanged obj) {
			_obj = obj ?? throw new ArgumentNullException(nameof(obj));
			_obj.PropertyChanged += PropertyChanged;
		}

		private void PropertyChanged(object sender, PropertyChangedEventArgs e) {
			if (!_subscriptions.TryGetValue(e.PropertyName, out var actions)) return;
			foreach (var action in actions) {
				if (action.Condition == null || action.Condition()) action.Action();
			}
		}

		public void Add(string propertyName, Action action) {
			if (!_subscriptions.TryGetValue(propertyName, out var actions)) {
				actions = new List<Entry> {new Entry(action)};
				_subscriptions.Add(propertyName, actions);
			} else {
				actions.Add(new Entry(action));
			}
		}

		public void Add(string propertyName, Func<bool> condition, Action action) {
			if (!_subscriptions.TryGetValue(propertyName, out var actions)) {
				actions = new List<Entry> {new Entry(condition, action)};
				_subscriptions.Add(propertyName, actions);
			} else {
				actions.Add(new Entry(condition, action));
			}
		}

		public void Dispose() {
			_obj.PropertyChanged -= PropertyChanged;
			_subscriptions.Clear();
		}


		private class Entry {
			public Entry(Action action) {
				Action = action;
			}

			public Entry(Func<bool> condition, Action action) {
				Condition = condition;
				Action = action;
			}

			public Func<bool> Condition { get; set; }
			public Action Action { get; set; }
		}
	}
}